The present invention relates to a piezoelectric transducer array for use in an ultrasonic imaging system particularly for medical diagnostic applications, and in particular to an arc scan type piezoelectric transducer array.
Ultrasonic transducer arrays are broadly classified under the categories of linear scan type and sector scan type. Conventional linear scan type arrays comprise piezoelectric transducers, 256 in number, which are successively linearly arranged side by side. A group of 16 transducers is selectively activated by delayed burst pulses generated by a commonly shared transmit circuitry so that a focused ultrasonic beam is transmitted. The selected group is successively shifted to the next by one transducer element to shift the beam linearly to the next, so that the ultrasonic energy is scanned in a rectangular format. Advantages of the liner scan imaging system are that it can hold the device size to a minimum due to the common sharing of transmit and receive circuitry among the transducers and that it can provide detailed near-field tomographic information. However, the linear scan system has a disadvantage in that it is incapable of scanning areas behind ribs and in that the transducer array is relatively bulky for manipulation.
Conventional transducer arrays of the sector scan type, on the other hand, usually comprise 32 transducer elements each of which is associated with its own transmit and receive circuitry. The transmit circuitry steers the ultrasonic beam in a sector format by applying successively delayed burst pulses to the transducers. Although the sector scan system is capable of obtaining tomographic information from behind ribs, the control circuitry is expensive due to the large number of circuit elements associated with the transducers and the near-field image is not satisfactory for diagnostic purposes.